Zoom projection lens system having a moveable positive component

ABSTRACT

A three-member zoom projection lens system whose front member is an airspaced negative doublet, whose central element is a positive cemented doublet, and whose rear member consists of three simple lenses and a cemented doublet, the central member being axially movable between the fixed front and rear members. A lens combining an f-number of 1.2 with a ratio of maximum and minimum focal lengths of 2.4 in a projector for Super-8 motion picture film can be obtained by maintaining certain parameters in the lens design.

United Statt [72] inventor Ladlslav Posplsil Vesellcko, Czechoslovakia Appl. No. 839,990

[22] Filed July 8, 1969 [45] Patented Sept. 28, 1971 FOREIGN PATENTS 4/1968 France Primary Examiner-John K. Corbin AnameyRichard Low Assignee Meopta narodni podnlk Prerov, Czechoslovakia [32] Priority July 12, 1968 [33] Czechoslovakia [31] PV 5120-68 ABSTRACT: A three-member zoom projection lens system whose front member is an airspaced negative doublet, whose [54] central element is a positive cemented doublet, and whose 4 Cl ll 1 D in F rear member consists of three simple lenses and a cemented a a doublet, the central member being axially movable between [52] US. the fixed front and rear members. A lens combining an number of 1.2 with a ratio of maximum and minimum focal lengths of 2.4 in a projector for Super-8 motion picture film can be obtained by maintaining certain parameters in the lens m .W 8 e d MMM M 8 "/5 0 W 3 3 0 G ZOOM PROJECTION LENS SYSTEM HAVING A EXAMPLE I MOVEABLE POSITIVE COMPONENT d M v This invention relates to zoom projection lenses, and par- 75.l3 ticularly to an improved design in a three-member lens systems of the type in which the first and third members are +263 fixed, the second member being axially movable, the first 115 member being an airspaced negative doublet consisting of a simple divergent lens and a simple convergent lens, and the +32": o I 67270 n 3 second member being a convergent cemented doublet. 47 o The known zoom projection lens systems of the type described have f-numbers of at least 1.3, and a ratio of not 7 o l "2 n I more than 1.7 between the maximum and minimum focal Rrnog. lengths. Further improvements need particularly in projectors 1.5 l.76ll2 26.5 for Super-8 motion picture film were achieved heretofore only 49 05 by relatively complex mechanical systems for shifting movable 2 a lens members. it.

The object of the invention is the provision of lens systems 5 l.67270 32.2 of the type described in which an increase in relative aperture over the limiting value indicated above and a wider variation 42-073 in focal lengths is achieved without losing the basic mechani- R cal simplicity of the original system. +5938 in the lens system of the invention whose parameters 4.5 l.62606 39.: selected within the ranges specified hereinbelow, an f-number 25 9a of L2 may be had in combination with a focal length ratio of 2.4 and a maximum angle of view of Furthermore, the R Petzval sum does not exceed a value of 0.2 for the smallest focal length, the longitudinal spherical aberration does not ex- 30 R ceed 0.08 mm., and the residual aberration due to field curva- -so.osa ture does not exceed 0.08 mm., over the entire range of focal 1677270 lengths. +169] A necessary condition for achieving the results outlined m above is a radius of curvature of the exposed convex surface of 35 m the convergent lens in the second member which is 1.3 to 1.7 240 mm 5 times the radius of the corresponding surface of the divergent R" lens in the second member. Furthermore, the front face of the divergent lens in the first or front member must have a radius EXAMpLE 2 of curvature 2to 3times the corresponding radius of the rear 40 face. Additionally, the first lens in the third member must be a 4 "1 negative, meniscus-shaped simple lens whose concavely arcuate front face has a radius of curvature smaller than that of any exposed surface in the first and second members and at least R L620 twice the radius of curvature of the rear surface in a cemented +295 doublet which, in combination with three airspaced simple 2.25 lenses, constitutes the third or rear member of the lens system. 36 0 The indicated relationship of radii of curvature is important in 4.0 1.67270 32.2 reducing the magnitude of the residual aberration, and per- R, mits the desired improvement to be achieved in conjunction with the use of suitable selected lens elements. R. w

The sole FlGURE of the drawing shows the general con- +7 9 struction of the lens system of the invention in conventional 0a L620" representation. L5 H5182 265 The fixed first or from member 1 consists of a simple, bicon- 1 cave lens and a meniscus shaped converging lens The axially R movable second or central member ll is a cemented doublet whose front component is biconvex, and whose rear com- 7210 32.2 ponent is a divergent meniscus, but the sequence of these 48 components may be reversed. The fixed third or rear member 60 consists, front to rear, of a divergent, meniscus shaped, simple R" lens, a biconvex simple lens, and cemented doublet whose +510 4.5 mzoos 394 front component rs brconvex and whose rear component rs R" biconcave, and a convergent, meniscus-shaped simple lens. 5 42.98 The nine lens elements have a combined total of 16 refractive 01 surfaces whose radii of curvature, in axial sequence, from to H3 8 rear, and are R, to R They have nine thicknesses, d,, d,, (1,, I 79 L653 503 11,, d,,, d,,, d,,,, d ,d,,, d and are separated by six airspaces d,, n 11., 11,, d,, d,,, d The radii of curvature, thicknesses, air- 3.3 l.67270 12.2 spacings, refractive indices and Abbe numbers V of four R representative, specific embodiments of the invention are +7.69l listed in the following examples. In these examples the numerical values or R and d are expressed in millimeters. All lenses H3 83 have and f-number of L2 and focal lengths variable between 14 503 12.5 and 30 mm. for an image of Super-8 motion picture for- R" mat.

EXAMPLE 3 It will be noted that the lens system whose parameters are given in example 3 deviates from the drawing in having a second or central member in which the front component is a divergent meniscus-shaped lens and the rear component is biconvex.

lclaim:

1. In a zoom projection lens system having fixedly spaced front and rear members, and a central member axially movable between said front and rear members, said first member being negative and said second and third members being positive, said first member consisting of a simple divergent lens element and a simple convergent lens element, the second member being a cemented doublet having a first convergent lens element and a second divergent lens element, and the third member consisting of five lens elements including three simple lens elements and one cemented doublet, the improvement which comprises:

a. the exposed surface of said first lens element having a radius of curvature 1.3 to 1.7 times the radius of curvalure of the exposed surface ot'suid second lens element; the front surface of the tllvergent 1011s in said first member having a radius ofcurvnture 2 to 3 limes the radius of curvature of the rear surface of said divergent lens;

c. the first lens of said third member being a negative,

meniscus-shaped simple lens having a negatively refractive surface of a radius of curvature smaller than the radius of curvature of any exposed surface in said first and second members and at least twice the radius of curvature of the rear surface of said cemented doublet in said third member.

2. In a lens system as set forth in claim 1, said member consisting of nine lens elements having a combined total of 16 refractive surfaces, the radii of curvature of said refractive surfaces, in axial sequence from to rear, being R, to R the 5 thicknesses of said nine lens elements being d (1,, d d 4,,

d d", d 1,, d, said nine lens elements constituting seven lenses separated by air spaces 11,, d 61 d d said radii of curvature, thicknesses, and airspaces having magnitudes, in consistent units of length, substantially as listed below, and said nine lens elements having indices of refraction n and Abbe number V substantially as listed below I 5 d "4 a 3. In a lens system as set forth in claim I, said members consisting of nine lens elements having a combined total of 16 refractive surfaces, the radii of curvature of said refractive surfaces, in axial sequence front to rear, being R to R the thicknesses of said nine lens elements being :1 11,, 11,, d d,, d d,,, d d said nine lens elements constituting seven lenses separated by air spaces 11,, d., 11 d,, d d said radii of curvature, thicknesses, and airspaces having magnitudes, in consistent units of length, substantially as listed below, and said nine lens elements having indices of refraction 11,, and Abbe number V, substantially as listed below l .5 l .620 I 60.3

said nine lens elements having indices of refraction n and Abbe number V substantially as listed below d n, V,

ao.osa 

1. In a zoom projection lens system having fixedly spaced front and rear members, and a central member axially movable between said front and rear members, said first member being negative and said second and third members being positive, said first member consisting of a simple divergent lens element and a simple convergent lens element, the second member being a cemented doublet having a first convergent lens element and a second divergent lens element, and the third member consisting of five lens elements including three simple lens elements and one cemented doublet, the improvement which comprises: a. the exposed surface of said first lens element having a radius of curvature 1.3 to 1.7 times the radius of curvature of the exposed surface of said second lens element; b. the front surface of the divergent lens in said first member having a radius of curvature 2 to 3 times the radius of curvature of the rear surface of said divergent lens; c. the first lens of said third member being a negative, meniscus-shaped simple lens having a negatively refractive surface of a radius of curvature smaller than the radius of curvature of any exposed surface in said first and second members and at least twice the radius of curvature of the rear surface of said cemented doublet in said third member.
 2. In a lens system as set forth in claim 1, said member consisting of nine lens elements having a combined total of 16 refractive surfaces, the radii of curvature of said refractive surfaces, in axial sequence front to rear, being R1 to R16, the thicknesses of said nine lens elements being d1, d3, d5, d6, d8, d10, d12, d13, d15, said nine lens elements constituting seven lenses separated by air spaces d2, d4, d7, d9, d11, d14, said radii of curvature, thicknesses, and airspaces having magnitudes, in consistent units of length, substantially as listed below, and said nine lens elements having indices of refraction nd and Abbe number Vd substantially as listed below d nd VdR1-75.131.51.6204160.3R2+26.9112.25R3+32.434.01.6727032.3 R4+ 147.20 47 to 4.2R5+65.667.01.6583257.1R6-22.0811.51.7618226.5R7- 49.052 to 44.8R8-22.0811.51.6727032.2R9- 42.0732.3R10+ 59.984.51.6260639.1R11-52.980.1 R12+ 13.1837.01.6584450.8R 13-30.0583.31.6727032.2R14+ 7.6911.1R15+ 13.1832.01.6584450.8R16+ 147.20
 3. In a lens system as set forth in claim 1, said members consisting of nine lens elements having a combined total of 16 refractive surfaces, the radii of curvature of said refractive surfaces, in axial sequence front to rear, being R1 to R16, the thicknesses of said nine lens elements being d1, d3, d5, d6, d8, d10, d12, d13, d15, said nine lens elements constituting seven lenses separated by air spaces d2, d4, d7, d9, d11, d14, said radii of curvature, thicknesses, and airspaces having magnitudes, in consistent units of length, substantially as listed below, and said nine lens elements having indices of refraction nd and Abbe number Vd substantially as listed below d nd VdR1- 60.01.51.6204160.3R2+ 29.5 2.25R3+ 36.04.01.6727032.2R4+270.047 to 4.2R5+70.07.01.6204160.3R6-22.0811.51.7618226.5R7- 43.02 to 44.8R8- 20.51.11.6727032.2R9-38.6510.1R10+ 52.04.51.6260639.1R11-42.980.1R12+13.87.01.6584450.8R13 - 30.0583.81.6727032.2R14+ 7.6912.7R15+ 13.1832.11.6584450.8R16+ 147.2
 4. In a lens system as set forth in claim 1, said members consisting of nine lens elements having a combined total of 16 refractive surfaces, the radii of curvature of said refractive surfaces, in axial sequence front to rear, being R1 to R16, the thicknesses of said nine lens elements being d1, d3, d5, d6, d8, d10, d12, d13, d15, said nine lens elements constituting seven lenses separated by airspaces d2, d4, d7, d9, d11, d14, said radii of curvature, thicknesses, and airspaces having magnitudes, in consistent units of length, substantially as listed below, and said nine lens elements having indices of refraction nd and Abbe number Vd substantially as listed below d nd VdR1- 75.131.51.6204160.3R2+ 26.9112.25R3+ 32.434.01.6727032.2R4+ 147.247 to 4.2R5+ 49.051.51.7618226.5R6+ 22.0817.01.6583257.1R7- 65.66to 44.8R8- 22.0811.51.6727032.2R9-38.6510.1R10+ 59.984.51.6260639.1R11-52.980.1R12+13.1837.01.6584450.8R13-30.0583.41.6727032.2R14+7.6913.1R15+ 13.1832.01.6584450.8R16+ 147.2 